Semiconductors are widely used in integrated circuits for electronic applications, including radios and televisions. Many integrated circuits now contain multiple levels of metallization for interconnections. A single semiconductor microchip may have thousands, and even millions of transistors. Logically, a single microchip may also have millions of lines interconnecting the transistors. These lines create a potential for electrical capacitance to gather in between the lines. As device geometries shrink and functional density increases, it becomes imperative to reduce the capacitance between the lines. If line-to-line capacitance builds up, a potential for electrical inefficiencies and inaccuracies exist. Reducing the RC time constant within these multi-level metallization systems will reduce the capacitance between the lines.
A method of reducing the RC time constant within these multi-level systems is the utilization of materials with low dielectric constants in the fabrication process. Conventional semiconductor fabrication uses silicon dioxide or similar insulating materials as both a gap filler between adjacent conductors at the same level and as an interlayer insulator. Silicon dioxide has a dielectric constant of about 3.9. This constant is based on a scale where 1.0 represents the dielectric constant of a vacuum. Various materials exhibit dielectric constants from very near 1.0 to values in the hundreds. As used herein, the term low-k will refer to a material with a dielectric constant less than 3.0.
Polymeric spin-on glass, polyimide, and various polymer low-k materials have been used in multilevel interconnect fabrication processes. The applications of these materials include low-k interlevel dielectric, dielectric gap fill, and local planarization. The conventional fabrication processes rely on thermal curing process after the material layer deposition to form a stable solid layer. However, the thermal curing process has been performed at 400-500 degrees Celsius.
In addition, the conventional method of manufacturing semiconductor devices has been by batch production. In contrast, only recently, have attempts focused on single wafer and continuous assembly line wafer manufacturing.